The surgical management of patients on anticoagulant therapy is often poorly understood in all fields of medicine (not just dentistry). Until now there has been no uniform approach to managing these patients and much of the advice routinely given by medical practitioners and haematologists has fallen behind the recent evidence. Many medical conditions from atrial fibrillation to prosthetic heart valves predispose patients to venous thrombosis and pulmonary embolism (Table 1). In order to prevent these complications, these patients are normally placed on an anticoagulant. By far the most common one in use is Warfarin, which is a derivative of 4 hydroxycoumarin.